gms | German Medical Science

Objective: Some pathologies such as spondylodiscitis, fractures or degenerative disease of the lumbar spine mandate internal fixation and anterior lumbar interbody fusion (ALIF). We compared the pre-/postoperative radiological findings after rigid and semi-rigid internal fixation with Titanium-alloy or Polyetheretherketone (PEEK) rods.

Methods: 49 consecutive patients (20 m, 29 f; mean age 67.27 ± 9.81 years (range 35-83)) who underwent ALIF at our department between February and December 2014 were included. We radiologically evaluated 84 segments L3/4 (n=13), L4/5 (n=37), L5/S1 (n=34). All patients underwent a baseline physical and neurological examination on admission. The diagnostic routine included MRI and CT scans and if possible, an upright x-ray of the lumbar spine before and after surgery. The local lordosis angle of the endplates and lumbar lordosis was measured. All patients received a primary posterior pedicle screw fixation, followed by insertion of a titanium cage over an anterior retroperitoneal approach (ALIF). A radiological assessment of the spinal geometry was performed and the differences between both groups were statistically analyzed.

Results: Average OR-time for the ALIF was 105.82 min ± 37.01 (35-188 min). The mean segmental lordosis angle prior to posterior fixation was 8.64 ± 5.96 degrees (-6.7 to 17) in the group with rigid (Titanium) posterior fixation (n=26) as opposed to 9.04 ± 4.15 degrees (0.8 - 17.2) in the semi-rigid (PEEK) group (n=23). After rigid posterior fixation, the segmental lordosis increased by a mean of 4.01 ± 1.98 degrees (1.5-10.7) significantly more than after semi-rigid posterior instrumentation (mean of 0.95 ± 0.57 degrees (-0.1 to 2.8)) (p<0.05). After ALIF, the segmental lordosis increased by a mean of 1.47 ± 1.04 degrees (-1.60-5.70) for the patients with Ti-alloy rods significantly less than in the patients with PEEK rods (mean 4.66 ± 0.85 degrees (-0.10–2.80)) (p<0.05). However, there was no significant difference between the final segmental lordosis in both groups (14.12 ± 5.17 rigid vs. 14.65 ± 3.90 semi-rigid). The initial lumbar lordosis was similar in both groups 47.18 ±15.19 vs. 48.61 ±11.07 (p=0.71), as was the final lumbar lordosis 52.77 ± 13.77 vs. 50.16 ± 11.05 (p=0.48).

Conclusion: Posterior fixation and ALIF seem to yield similar results in terms of final segmental and lumbar lordosis. The semi-rigid PEEK rod system seems to allow less lordosis correction during posterior fixation compared to the rigid titanium-alloy rod system but this can be compensated by a higher lordosis correction through the ALIF procedure.